Browsing by Subject "Hand"

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    Hand force profiles of women with hand osteoarthritis during sealed jar opening
    (2014-10) McGee, Corey Weston
    Purposes: Joint protection strategies are often recommended for individuals with hand arthritis. However, there is little research regarding their effectiveness or on the use of measures in evaluating the effects of joint protection strategies. The purposes of this study were to 1) evaluate the effects of the type of grasp, the hand grasping the lid, and the use of non-skid material on the hand forces acting upon a jar lid when breaking a jar's seal, 2) examine the hand forces requirements when opening a sealed jar and 3) investigate relationships between several measures of hand function and the actual hand forces used during the everyday task of opening a sealed jar in order to validate their use in measuring the effectiveness of joint protection strategies such as using a counterforce such as a table or opposing extremity and using a nonskid material.Methods: A novel jar device created by McGee, Nuckley, and Mathiowetz was used to gather measurements of grip force, compressive force down through the lid's axis of rotation (Fz) and compressive force perpendicular to the side of the lid (Fx/Fy) when attempting to open a `sealed jar'. The jar lid's torque requirement was set to 4.24 N*m, a torque commonly imposed by the manufacturer when creating a seal on larger diameter jars. Thirty-one women with hand osteoarthritis were asked to complete 16 jar opening simulations by alternating three different factors: hand turning the jar lid, position (supinated/vertical and oblique/diagonal), and use of a non-skid material. After each jar turning simulation, participants were asked to report their perceived level of pain and exertion using the 0 to 10 scales of the NRS and Borg CR10, respectively. Additional measures of hand function were quantified to determine if and to what extent they predicted success and the capacity to generate forces when opening a sealed jar.Results: The impact of arthritis on our sample's function was modest (AIMS2-SF2 Total Health Score; x = 10.62) and the distribution of arthritis between hands was not dissimilar. Use of the supinated grasp required less force/time in Fx [F(1,419)=30.5, p<.0001], Fy [F(1,419)=34.5, p<.0001], and Fz than power grasp [F(1,419)=23.5, p<.0001]. Participants used less grip force to twist the lid with their left hand than with their right hand [F(1,419)=21.7, p<.0001]. Participants also perceived their effort to be less when using their left hand, a supinated grasp, and non-skid material. Additionally, participants rated their pain as lower when using their left hand and when using a supinated grasp. Lastly, a left supinated grasp with a non-skid material was a significantly more successful strategy to open jars than was any other (χ2=9.4, p<.001). Across all approaches, participants who were successful used 149.2±6.2 N of grip force and 47.8±2.8 N of `compensatory' forces when opening the sealed jar. Perceived effort was a significant positive predictor of grip force across time and is a significant negative predictor of peak M(z). Palmar abduction of the stabilizing thumb was a significant positive predictor of torque and a negative predictor of grip forces. Total active motion of the stabilizing and turning thumbs was a positive predictor of grip force and an increase in pain from baseline was a significant negative predictor of grip force and a positive predictor of torque.Conclusions: The counterforce offered by the supinated `stabilizing' hand results in the use of fewer compensatory forces by the turning hand. The left hand requires less grip force to successfully open a sealed jar and pain as well as perceived effort were least among those who used a non-skid material when opening. This data supports that women with hand arthritis will know more success, perceive less pain and effort, use less grip force, and will more efficiently generate the forces required to break the seal of a large jar when using a left hand, supinated counterforce, and non-skid material. These findings validate the use of non-skid material to reduce hand forces with jar turning but only when combined with a supinated approach. Perceived effort, and a change in pain from baseline are strong predictors of the forces used during jar opening and thus should be considered when considering the effectiveness of joint protection strategies used by women with hand osteoarthritis when attempting to open sealed jars. Other measures of hand function were also predictive of the hand forces generated when opening a sealed jar and these factors should be considered during assessment and intervention planning.
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    Hand Images in Virtual Spatial Collaboration for Traffic Incident and Disaster Management
    (Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2013-03) Drew, Daniel; Hayes, Caroline C.; Nguyen, Mai-Anh; Cheng, Xuan
    To develop demonstration technology that can overlay hand videos on spatial images such as traffic maps, and assess the impact of this technology on virtual collaboration. This work explores to what degree gestures impact collaboration effectiveness in the task of traffic incident management, with the goal of informing design of tools to support virtual collaboration in this domain. Methods: Eighteen participants worked in pairs to solve three traffic incident scenarios using three different interaction approaches: 1) face-to-face: participants worked together by marking up an electronic map projected on the table in front of them; 2) separated: participants were separated by a soft wall while they worked together on the electronic map with electronic drawing tools; or 3) hand images: same as 2 with the addition of the partner’s hand images projected on the map. Participants were video recorded. The questionnaires were given to participants after each trial to evaluate workload, positive interactions, team behaviors, connection to teammate, and frustration. Results: Participants spent more time on the task and perceived a higher level of time pressure when using hand images than when working face-to-face. When working face-to-face, participants felt more like their teammate was at the same table and felt less disconnected from their teammate than when working separately or using hand images. Conclusions: The results indicate that adding hand videos to a virtual drawing tool for the task of traffic incident management can increase team behaviors and change the way in which team members communicate information.
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    Neural control strategies for a complex biomechanical system: primary motor cortex and the hand.
    (2010-03) Prosise, Jodi Fae
    The hand is a complex biomechanical apparatus with 27 bones, 18 joints, and 39 intrinsic and extrinsic muscles, resulting in over 20 degrees of freedom. Despite significant mechanical coupling between the joints of the hand, humans and non-human primates are able to perform both simple and highly intricate movements of the hand and fingers. Much of this ability is attributed to the neural control mechanisms. Although a large number of cortical and subcortical systems are involved in prehension, the primary motor cortex (M1) plays a critical role in reaching to and grasping an object. The strategy utilized by M1 to control movements of the hand is of considerable interest in the fields of neuroscience and engineering. A major area of debate is whether M1 explicitly controls individual degrees of freedom or more global patterns of movement. To test this hypothesis, two rhesus monkeys were trained to reach and grasp a set of 23 different objects that were designed to systematically vary hand shape. Fourteen joint angles and angular velocities of the hand and fingers were monitored simultaneously with the recording of 81 single cells in the hand area of M1. The joint angles were significantly different across objects during the reach and grasp epochs, indicating that the hand preshaped to match properties of the object to be grasped. There were fewer instances of significant differences in joint angular velocities across objects than for the joint angles, especially during the premove and grasp epochs. Singular value decomposition (SVD) analyses defined a dominant hand shaping pattern that was similar across sessions and monkeys that consisted of simultaneous extension/flexion of the MCP and IP joint angles. The majority of the variation in hand shaping was captured by only a few lower-order eigenvectors (EVs), suggesting that they represent major patterns of hand shaping. In contrast, the higher-order EVs characterize the more detailed movements of the hand because of the smaller amount of variance captured. Linear regression analysis revealed that the firing of many M1 cells (up to 38.6%) was highly correlated with individual joint angles with only limited correlation to joint angular velocities. Typically, a cell's firing was correlated with multiple joints. The firing of M1 cells was also highly correlated to the lower-order temporal weighting vectors (TWs) derived from SVD analyses. Higher-order TWs were not well-represented. In addition, most cells displayed high R2-values for multiple lower-order TWs. Correlations were improved most often by incorporating a temporal lead in the neural firing. This suggests that M1 is involved with the control of dominant hand shaping patterns rather than explicitly controlling details. These findings could be used to develop brain-machine interface algorithms in which signals from M1 are used to control robotic or virtual hands.